Light-emitting device

ABSTRACT

A light-emitting device of the present invention includes: a LED chip  10 ; a chip mounting member  70  having a conductive plate (heat transfer plate)  71  one surface side of which the LED chip  10  is mounted on and a conductor patterns  73, 73  which is formed on the one surface side of the conductive plate  71  through an insulating part  72  and electrically connected to the LED chip  10 ; and a sheet-shaped connecting member  80  disposed on the other surface side of the conductive plate  71  to connect the conductive plate  71  to a body of the luminaire  90  which is a metal member for holding the chip mounting member  70 . The connecting member  80  is made of a resin sheet which includes a filler and whose viscosity is reduced by heating, and the connecting member  80  has an electrical insulating property and thermally connects the conductive plate  71  and the body  90  of the luminaire to each other.

TECHNICAL FIELD

The present invention relates to a light-emitting device.

BACKGROUND ART

Conventionally, light-emitting devices which emits light having adifferent color from the emission color of a LED chip by combining theLED chip and a phosphor (e.g., fluorescent pigment and fluorescence dye)as a wavelength converting material which emits light having an emissioncolor different from that of the LED chip when excited by the lightemitted by the LED chip have been researched and developed at variousplaces. Such light-emitting devices include a commercialized whitelight-emitting device (which is generally called a white LED) in whichan LED chip for emitting blue light or ultraviolet light is combinedwith a phosphor to produce a white light (emission spectrum of whitelight).

Also, the application of white LEDs to a luminaire has become an activearea for research and development in accordance with recent high outputof white LEDs, but when the white LED is applied to an application whichrequires a relatively high light output such as general illumination, adesired light output cannot be produced by only one white LED. So,generally, a plurality of white LEDs are mounted on one circuit board toform an LED unit (light-emitting device), and the LED unit ensures thedesired light output as a whole (for example, see Japanese PatentApplication Laid-Open No. 2003-59332 (hereinafter, referred to as PatentDocument 1)).

Also, conventionally, in the light-emitting device having an LED chipand a circuit board on which the LED chip is mounted, a structure foreffectively dissipating heat generated in a light-emitting part of theLED chip to the outside has been proposed so as to increase the power ofthe light output by constraining a rise of a junction temperature of theLED chip and increasing the input power (for example, see JapanesePatent Application Laid-Open No. 2003-168829 (hereinafter, referred toas Patent Document 2), Paragraph [0030] and FIG. 6).

In the light-emitting device disclosed in Patent Document 2, as shown inFIG. 12, a metal substrate in which a conductor pattern 203 is formedvia an insulating resin layer 202 on a metal plate 201 is adopted as acircuit board 200 on which LED chips 10′ are mounted, so that the heatgenerated at each of the LED chips 10′ can be transferred to the metalplate 201 through a heat transfer member 210. In this case, each of theLED chips 10′ is a GaN-based blue LED chip in which a light-emittingpart made of a GaN-based compound semiconductor material is formed onone surface side of a substrate for crystal growth formed from asapphire substrate which is an insulator, and each LED chip 10′ ismounted on the circuit board 200 by flip chip, and the other surface ofthe substrate for crystal growth is a light output surface.

When the light-emitting device having a configuration shown in FIG. 12is applied to a luminaire, in order to efficiently dissipate heatgenerated in the light-emitting device, it is conceivable that the bodyof the luminaire for holding the circuit board 200 on which the LEDchips 10′ are mounted is made of a metal, and the metal plate 201 of thecircuit board 200 of the light-emitting device is thermally connected tothe metal body of the luminaire. However, in order to ensure a lightingsurge protection, it is necessary to interpose a heat radiation sheethaving a rubber sheet shape, such as Sarcon (registered trademark), as asheet-shaped insulating layer, between the body of the luminaire and themetal plate 201 of the circuit board 200, so the heat resistance fromthe light-emitting part of each LED chip 10′ to the body of theluminaire, which is the metal member, for holding the light-emittingdevice is increased. Therefore, it is necessary to limit the input powerto each LED chip 10′ to prevent the junction temperature of each LEDchip 10′ from rising above the maximum junction temperature, so it isdifficult to increase the power of the light output.

In addition, when the above-mentioned heat radiation sheet is interposedbetween the metal plate 201 and the body of the luminaire, the heatradiation sheet may cause lack of adhesion between the metal plate 201and the heat radiation sheet, which may lead to an increased heatresistance due to air spaces generated between the sheet and the plate,or which may lead to various heat resistances between each of thelight-emitting devices and the body of the luminaire.

Furthermore, in the light-emitting device disclosed in Patent Document2, since the heat generated in the light-emitting part of the LED chip10′ is transferred to the metal plate 201 via the heat transfer member210 having a size smaller than that of the LED chip 10′, the heatresistance from the LED chip 10′ to the metal plate 201 is relativelyhigh. Therefore, when the sapphire substrate, that is the substrate forcrystal growth, is mounted on the metal plate 201 to be thermallyconnected, there is a problem that the heat resistance of the sapphiresubstrate is increased.

DISCLOSURE OF THE INVENTION

The present invention was made in view of above situation, and theobject of the present invention is to provide a light-emitting devicewhich can constrain an increase in temperature of an LED chip and canincrease a power of the light output.

A light-emitting device of the present invention includes: an LED chip,a chip mounting member, and a sheet-shaped connecting member. The chipmounting member has a heat transfer plate and a conductor pattern. Theheat transfer plate is made of a heat conductive material and onesurface side of which the LED chip is mounted on. The conductor patternis formed on the one surface side of the heat transfer plate through aninsulating part and electrically connected to the LED chip. Thesheet-shaped connecting member is disposed on the other surface side ofthe heat transfer plate to connect the heat transfer plate to a metalmember for holding the chip mounting member, and the sheet-shapedconnecting member has an electrical insulating property and connects theheat transfer plate and the metal member thermally to each other.

In the light-emitting device of the present invention, because thesheet-shaped connecting member which is disposed on the other surfaceside of the heat transfer plate to connect the heat transfer plate to ametal member for holding the chip mounting member and has an electricalinsulating property and thermally connects the heat transfer plate andthe metal member to each other is provided, it is possible to lessen aheat resistance from the light-emitting part of the LED chip to themetal member for holding the chip mounting member as compared with acase where a rubber sheet-shaped heat radiation sheet is interposed.Therefore, it is possible to increase the heat radiation property andreduce the variation of heat resistances, and it is possible toconstrain a rise of a junction temperature of the LED chip. As a result,it is possible to increase the input power to increase a power of thelight output. Furthermore, when the light-emitting device is used at thesame light output as that of the prior art, it is possible to reduce thejunction temperature of the LED chip as compared to that of the priorart. So, it has an advantage that the life span of the LED chip can beextended.

Preferably, the LED chip has a light-emitting part made of a GaN-basedcompound semiconductor material on a main surface side of a conductivesubstrate formed from a SiC substrate or a GaN substrate.

In this case, it is possible to set a lattice constant of a substratefor crystal growth of the LED chip close to that of the GaN-basedcompound semiconductor material, and, because the substrate for crystalgrowth has conductivity, it is possible to form an electrode on thesubstrate for crystal growth, In addition, as compared with a case wherethe substrate for crystal growth is a sapphire substrate, the heattransfer property of the substrate for crystal growth is superior, so itis possible to reduce the heat resistance of the substrate for crystalgrowth. Therefore, it is possible to improve the heat radiationproperty.

Preferably, the light-emitting device further includes a sub-mountmember which is larger in chip size than the LED chip and is disposedbetween the LED chip and the heat transfer plate to relieve a stressapplied to the LED chip due to a difference in linear expansioncoefficient between the LED chip and the heat transfer plate.

In this case, it is possible to prevent the LED chip from being damageddue to the difference in linear expansion coefficient between theconductive substrate and the heat transfer plate of the LED chip.Therefore, it is possible to increase the reliability of the chip.

Preferably, the connecting member is made of a resin sheet whichincludes a filler and whose viscosity is reduced by heating.

In this case, the problem that lack of adhesion between the chipmounting member and the connecting member produces air spaces betweenthe chip mounting member and the connecting member and increases theheat resistance, or the problem that aging degradation of the connectingmember produces a gap between the chip mounting member and theconnecting member and increases the heat resistance can be prevented.

Preferably, the connecting member is configured to have a plane sizelarger than that of the heat transfer plate.

In this case, as compared with a case where the connecting member andthe heat transfer plate have the same plane size, it is possible tolengthen a creepage distance between the heat transfer plate and themetal member, so that it is possible to enhance a lighting surgeprotection when the device is used as a light source of a luminaire.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing main sections of alight-emitting device in accordance with a first embodiment of thepresent invention when the device is mounted on a body of a luminaire;

FIG. 2 is a schematic exploded perspective view of the light-emittingdevice of FIG. 1;

FIG. 3 is a schematic side view, partially broken away, of the luminaireof FIG. 1;

FIG. 4 is a schematic perspective view showing main sections of theluminaire;

FIG. 5 is a schematic cross-sectional view showing a light-emittingdevice in accordance with a second embodiment of the present invention;

FIG. 6 is a schematic exploded perspective view showing main sections ofa luminaire which uses the light-emitting device of FIG. 5;

FIG. 7 is a view illustrating a method for manufacturing thelight-emitting device of FIG. 5;

FIG. 8A is a view illustrating main sections of the light-emittingdevice of FIG. 5;

FIG. 8B is a view illustrating main sections of the light-emittingdevice of FIG. 5;

FIG. 9 is a schematic exploded perspective view of the light-emittingdevice of FIG. 5;

FIG. 10 is a schematic exploded perspective view showing main sectionsof a luminaire which uses the light-emitting device of FIG. 5;

FIG. 11 is a schematic perspective view showing main sections of aluminaire which uses the light-emitting device of FIG. 5; and

FIG. 12 is a schematic cross-sectional view of a light-emitting device(LED unit) in the prior art.

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

Hereinafter, a light-emitting device of the present embodiment will beexplained with reference to FIG. 1 to FIG. 4.

A light-emitting device (LED chip unit) 1 of the present embodiment isused as a light source of a luminaire, and includes: an LED chip 10 in aform of a rectangular plate, a chip mounting member 70, a sub-mountmember 30, a reflector (reflecting device) 50, a protective cover 60,and a sheet-shaped connecting member 80. The chip mounting member 70 hasa conductive plate 71 in a form of a rectangular plate and conductorpatterns (lead patterns) 73, 73. The conductive plate 71 is formed tohave a chip size larger than that of the LED chip 10, and the LED chip10 is mounted to one surface side of the conductive plate 71. Theconductor patterns 73, 73 are formed on the one surface side of theconductive plate 71 through an insulating part 72 and electricallyconnected to the LED chip 10. The sub-mount member 30 is disposedbetween the conductive plate 71 and the LED chip 10 for relieving astress applied to the LED chip 10 due to a difference in linearexpansion coefficient between the conductive plate 71 and the LED chip10. The reflector 50 is disposed on one surface of the chip mountingmember 70 in such a way that it surrounds the LED chip 10 for reflectingthe light emitted from the side surfaces of the LED chip 10 toward thefront of the LED chip 10 (upward in FIG. 1). The protective cover 60 isattached to front of the reflector 50 to cover the LED chip 10. Thesheet-shaped connecting member 80 is disposed on the other surface sideof the conductive plate 71 to connect the conductive plate 71 to a metalbody 90 of the luminaire for holding the chip mounting member 70, and ithas an electrical insulating property, and it thermally connects theconductive plate 71 and the body 90 of the luminaire to each other. Inthe present embodiment, the body 90 of the luminaire is the metal memberfor holding the chip mounting member 70, but any metal member other thanthe body 90 of the luminaire may be used to hold the chip mountingmember 70. The metal member may be formed of a material having a highheat conductivity, such as Al and Cu. In the present embodiment, thechip mounting member 70, the reflector 50, and the protective cover 60form a package of the LED chip 10. And, in the present embodiment, theconductive plate 71 is a heat transfer plate which is made of a heatconductive material and one surface side of which the LED chip 10 ismounted on.

The luminaire in the present embodiment is used as a spotlight forexample, and a rotation base 110 is fixed to a support table 100, and anarm 112 is coupled to the rotation base 110 at one end thereof using ashaft screw 111, and the body 90 of the luminaire is coupled to the arm112 using a threaded screw 113.

In the luminaire of this embodiment, as shown in FIG. 3 and FIG. 4, thebody 90 has a cylindrical shape having a bottom and an opening on theother side of the bottom, and the plurality of light-emitting devices 1are housed in the body 90. In the luminaire of this embodiment, each ofthe light-emitting devices 1 is mounted on a bottom wall 90 a of thebody 90 through the connecting member 80, and the opening of the body 90is closed by a front cover 91. The front cover 91 includes a translucentplate 91 a made of a circular glass plate, and a ring-shaped windowframe 91 b for holding the translucent plate 91 a, and the ring-shapedwindow frame 91 b is attached to the body 90. The translucent plate 91 ais not limited to a glass substrate, but may be made of any translucentmaterial. And, the translucent plate 91 a may integrally include a lensfor controlling the distribution of light emitted from each of thelight-emitting devices 1.

The plurality of light-emitting devices 1 housed in the body 90 areconnected in series to each other by a plurality of leads 93 (see FIG. 1and FIG. 3), and the leads 93 on both ends of a series circuit of theplurality of light-emitting devices 1 are inserted into an insertionhole 90 c formed through the bottom wall 90 a of the body 90 to receivepower from a power source circuit (not shown). As the power supplycircuit, for example, a power supply circuit having a rectifier circuitusing a diode bridge for rectifying and smoothing an AC output from anAC power source such as a commercial power supply, and a smoothingcapacitor for smoothing the output of the rectifier circuit may beadopted. In the present embodiment, the plurality of light-emittingdevices 1 in the body 90 of the luminaire are connected in series, butthe connection relation of the plurality of light-emitting devices 1 isnot limited to that. For example, the light-emitting devices 1 may beconnected in parallel, or a series connection and a parallel connectionmay be combined.

The LED chip 10 is a GaN-based blue LED chip which emits blue light, andas the substrate for crystal growth, used is a conductive substrate 11made of an n-type SiC substrate which has a lattice constant and acrystal structure that are closer to those of GaN, as compared to thoseof a sapphire substrate, and has a conductivity. A light-emitting part12, which is made of a GaN-based compound semiconductor material and hasa multi-layered structure such as double-heterostructure, is grown byepitaxial growth method (for example, MOVPE method) on a main surfaceside of the conductive substrate 11. A cathode electrode (n-Typeelectrode) (not shown) is formed on a back surface of the conductivesubstrate 11, and an anode electrode (p-Type electrode) (not shown) isformed on a front surface of the light-emitting part 12 (an outermostsurface on the main surface side of the conductive substrate 11). Inshort, the LED chip 10 has an anode electrode formed on one surfacethereof, and a cathode electrode formed on the other surface thereof.The cathode electrode and the anode electrode have a multi-layeredstructure having a Ni film and an Au film, but the material of thecathode electrode and the anode electrode is not limited to that, andthe cathode electrode and the anode electrode may be made of anymaterial which can obtain a high Ohmic characteristic, such as Al.

In the LED chip 10, the anode electrode is electrically connected to oneend (inner lead part) of one conductor pattern 73 on the chip mountingmember 70 through a bonding wire 14 (a left bonding wire 14 in FIG. 1);the cathode electrode is electrically connected to one end (inner leadpart) of the other conductor pattern 73 on the chip mounting member 70through the sub-mount member 30 and a bonding wire 14 (a right bondingwire 14 in FIG. 1), and the other end of each conductor pattern 73 iselectrically connected to the lead 93 via a connecting part 95 made ofsolder.

In the chip mounting member 70, as a material of the conductive plate71, a conductive material having a conductive property and a relativelyhigh thermal conductivity, such as Cu and phosphor bronze, may beadopted, and as a material of the conductor patterns 73, 73, Cu may beadopted, for example. As a material of the insulating part 72 of thechip mounting member 70, a resin having an insulating property, such asglass epoxy resin such as FR-4, polyimide-based resin, and phenol resinmay be adopted. In the present embodiment, the chip mounting member 70is provided with window hole 75 at the center of the insulating part 72for partially exposing a surface of the conductive plate 71, and the LEDchip 10 is mounted to the conductive plate 71 through the sub-mountmember 30 disposed inside the window hole 75. The conductive plate 71only has to have about the same thickness as that of a lead frame.Therefore, as compared with the circuit boards of the light-emittingdevices disclosed in the above Patent Documents 1 and 2, it is possibleto reduce the thickness of the circuit board.

In the present embodiment, the light-emitting part 12 of the LED chip 10is mounted to the conductive plate 71 in such a way that thelight-emitting part 12 is positioned on a side further away from theconductive plate 71 than the conductive substrate 11. But, thelight-emitting part 12 of the LED chip 10 may be mounted to theconductive plate 71 in such a way that the light-emitting part 12 ispositioned on a side closer to the conductive plate 71 than theconductive substrate 11. In terms of the light output efficiency, it isdesired that the light-emitting part 12 is disposed on the side awayfrom the conductive plate 71. But, since the conductive substrate 11 andthe light-emitting part 12 have similar refractive indexes in thepresent embodiment, even if the light-emitting part 12 is disposed onthe side near the conductive plate 71, it does not result in asubstantial drop of the light output efficiency.

The reflector 50 has a frame shape having a circular opening therein.The opening has an opening area which increases as the distance from theLED chip 10 increases in the thickness direction of the LED chip 10. Thereflector 50 is fixedly attached to the chip mounting member 70 by usinga fixing member 55 made of a sheet-shaped adhesive film having aninsulating property.

As a material of the reflector 50, a material which has a relativelyhigh reflectivity with respect to the light (blue light in the presentinvention) emitted from the LED chip 10, for example, Al, may beadopted. The fixing member 55 has a circular opening 55 a formed thereinwhich corresponds to the opening of the reflector 50. It is desired thata transparent encapsulation resin (for example, silicone resin) forsealing the LED chip 10 is potted in the reflector 50.

The protective cover 60 includes: a dome-shaped cover section 62 withthe center being positioned on the central line along the thicknessdirection of the LED chip 10; and a projected flange section 61 which iscontinuously and integrally formed with the peripheral edge of anopening of the cover section 62. An annular positioning rib 61 a isprotruded from the periphery of the surface of the flange section 61 onthe side toward the reflector 50 so that the protective cover 60 can bestably positioned relative to the reflector 50. The protective cover 60may be attached to the reflector 50 using an adhesive (for example,silicone resin, and epoxy resin) for example.

The protective cover 60 is a molding of a mixture of a translucentmaterial, such as silicone, and a particulate yellow phosphor which isexcited by the blue light emitted from the LED chip 10 and emits broadyellowish light. Therefore, in the light-emitting device 1 of thepresent embodiment, the protective cover 60 also functions as a colorconversion part which emits a light having a color different from theemission color of the LED chip 10 when excited by the light emitted fromthe LED chip 10, so that the entire light-emitting device 1 composes awhite LED for outputting a white light which is a combination of theblue light emitted from the LED chip 10 and the light emitted from theyellow phosphor. The translucent material of the protective cover 60 isnot limited to silicone, and may be acrylic resin, epoxy resin, or glassfor example. The phosphor which is mixed with the translucent materialused for the protective cover 60 is not limited to the yellow phosphor.For example, a red phosphor and a green phosphor may be mixed with thetranslucent material to obtain the white light. When the emission colorof the LED chip 10 is the same color as a desired emission color of thelight-emitting device 1, it is not necessary to mix a phosphor to thetranslucent material.

In the present embodiment, as described above, the LED chip 10 is a blueLED chip having a blue emission color, and the conductive substrate 11is a SiC substrate. But, a GaN substrate may be used as a substitute forthe SiC substrate. In the case where a SiC substrate or a GaN substrateis used, as seen from Table 1 below, as compared with the case where asapphire substrate, which is an insulator, is used as the substrate forcrystal growth as above-mentioned Patent Document 2, the thermalconductivity of the substrate for crystal growth is high, and the heatresistance thereof is low. The emission color of the LED chip 10 is notlimited to blue, but may be red or green. That is, the material of thelight-emitting part 12 of the LED chip 10 is not limited to a GaN-basedcompound semiconductor material, but a GaAs based compound semiconductormaterial or GaP based compound semiconductor material may be useddepending on an emission color of the LED chip 10. Also, the conductivesubstrate 11 is not limited to a SiC substrate, and may be selected froma GaAs substrate, a GsP substrate, and the like depending on a materialof the light-emitting part 12.

TABLE 1 Thermal Coefficient of Linear Heat Substrate For ConductivityExpansion Resistance Crystal Growth [W/m · K] [×10⁻⁶/K] [K/W] 6H—SiC 3504.2 0.857 GaN 130 5.59 2.308 GaP 110 4.65 2.727 GaAs 54 5.9 5.556Sapphire 42 5.3 7.143

The LED chip 10 is formed into the rectangular plate shape having a chipsize larger than that of the LED chip 10 as described above, and ismounted to the conductive plate 71 through the sub-mount member 30 forrelieving a stress which is applied to the LED chip 10 due to adifference in linear expansion coefficient between the LED chip 10 andthe conductive plate 71. The sub-mount member 30 functions not only torelieve the stress applied to the LED chip 10, but also to transfer theheat generated at the LED chip 10 to a wider area of the conductiveplate 71 than the chip size of the LED chip 10. Therefore, it ispreferable that the surface area of the conductive plate 71 on the LEDchip 10 side is adequately larger than that of the LED chip on the chipmounting member 70 side. For example, in order to efficiently waste theheat from the LED chip 10 of 0.3 to 1.0 mm squared, it is preferablethat the contact area between the conductive plate 71 and the connectingmember 80 is increased and the heat resistance is reduced bytransferring the heat of the LED chip 10 uniformly to a wide area, andit is desired that the surface area of the conductive plate 71 on theLED chip 10 side is more than ten times that of the LED chip 10 on theconductive plate 71 side. The sub-mount member 30 only has to relieve astress applied to the LED chip 10, and since the thickness dimension ofthe sub-mount member 30 can be made smaller than those of circuit boardsof the light-emitting devices disclosed in the above Patent Documents 1and 2, it is possible to reduce the heat resistance by adopting amaterial having a relatively high thermal conductivity.

In this embodiment, the sub-mount member 30 is made of CuW. And, in theLED chip 10, as described above, the anode electrode is electricallyconnected to one conductor pattern 73 via the bonding wire 14 and thecathode electrode is electrically connected to the other conductorpattern 73 via the sub-mount member 30 and another bonding wire 14.

The material of the sub-mount member 30 is not limited to CuW, and forexample as seen from Table 2 below, any material having a linearexpansion coefficient which is relatively close to that of 6H-SiC, thatis the material of the conductive substrate 11, and a relatively highthermal conductivity may be used, such as W, AIN, composite SiC, and Si.When the sub-mount member 30 is formed of an insulator such as AIN andcomposite SiC, for example, an electrode pattern may be convenientlyprovided on the surface of the sub-mount member 30 on LED chip 10 sideto be connected with the cathode electrode, and the electrode patternmay be electrically connected with the other conductor pattern 73 viathe bonding wire 14.

TABLE 2 Coefficient of Thermal Linear Expansion conductivity Materials[×10⁻⁶/K] [W/m · K] Material of 6H—SiC 4.2 350 Substrate For GaN 5.59130 Crystal Growth GaP 4.65 110 GaAs 5.9 54 Sapphire 5.3 42 Material ofSub- Al 23.2 237 mount Member Cu 16.6 398 W 4.5 178 CuW 6.4 160 Si 2.6168 AlN 4.6 165 Alumina 7.1 29 Connecting Au 14.2 315 Material 63Sn—37Pb21.0 50 Silver Paste 70.0 1.1

In a case where the conductive plate 71 is made of Cu, it is possible toconnect the sub-mount member 30 and the conductive plate 71 directly toeach other, when CuW or W is adopted as the material of the sub-mountmember 30. In that case, as shown in Table 3 below, as compared with acase where the sub-mount member 30 and the conductive plate 71 areconnected to each other using a brazing material for example, it ispossible to increase the connection area between the sub-mount member 30and the conductive plate 71 and reduce the heat resistance at theconnection part therebetween. The LED chip 10 and the sub-mount member30 may be connected to each other using a Pb-free solder such as AuSnand SnAgCu, but when AuSn is used for the connection, the surface of thesub-mount member 30 for the connection should be subjected to apretreatment for forming a metal layer of Au or Ag in advance.

TABLE 3 Brazing Direct Connection Connecting Area 60-80% Almost 100%Connecting Strength 98 N/mm² or more 127 N/mm² or more Shear Strength 98N/mm² 127 N/mm² Connecting Part Flux is sometimes left.

When the sub-mount member 30 is made of W and the sub-mount member 30and the conductive plate 71 are connected to each other directly, asseen from Table 4 below, the thermal conductivity is increased and theheat resistance can be reduced therebetween, as compared with a casewhere the sub-mount member 30 and the conductive plate 71 are connectedto each other using silver solder. When the conductive plate 71 is madeof Cu and the sub-mount member 30 is made of AIN, composite SiC, or thelike, the conductive plate 71 and the sub-mount member 30 may beconnected to each other using a Pb-free solder such as AuSn and SnAgCu,but when AuSn is used for the connection, the surface of the conductiveplate 71 for the connection should be subjected to a pretreatment forforming a metal layer of Au or Ag in advance.

TABLE 4 Ag Brazing Direct Connection Thermal Conductivity 185.4 211.8[W/m · K]

By the way, the light-emitting device 1 of the present embodimentincludes, as described above, the sheet-shaped connecting member 80disposed on the other surface side of the conductive plate 71 to connectthe conductive plate 71 to the metal body 90 of the luminaire forholding the chip mounting member 70 and having an electrical insulatingproperty and thermally connecting the conductive plate 71 and the body90 of the luminaire to each other is provided, and the light-emittingdevice 1 is connected to the body 90 of the luminaire through theconnecting member 80. That is, in the luminaire of the presentembodiment, the sheet-shaped connecting member 80 is interposed betweenthe conductive plate 71 of the chip mounting member 70 of eachlight-emitting device 1 and the body 90 of the luminaire which is ametal member, and the connecting member 80 has a function of providingelectrical isolation between the conductive plate 71 and the body 90 ofthe luminaire and also of thermally connecting both of them to eachother.

If a heat radiation sheet of the prior art is interposed betweenconductive plate 71 and the body 90 of the luminaire, the heat radiationsheet may cause lack of adhesion between the conductive plate 71 and theheat radiation sheet, which may result in an increase of the heatresistance due to air spaces generated between the sheet and the plate,or which may result in various heat resistances between each of thelight-emitting devices 1 and the body 90 of the luminaire.

To the contrary, in the light-emitting device 1 of the presentembodiment, the sheet-shaped connecting member 80 is made of a resinsheet (for example, an organic green sheet such as an epoxy resin sheetwhich is highly filled with fused silica) which includes a filler, suchas silica and alumina, and whose viscosity is reduced by heating. So,the member 80 has an electrical insulating property, a high thermalconductivity, a high flowability in heating, and a high adhesionproperty to convex-concave surfaces. Therefore, it is possible toprevent the generation of an air space (air gap) between the connectingmember 80 and the conductive plate 71 and between the connecting member80 and the body 90 of the luminaire when the conductive plate 71 isconnected to the metal body 90 of the luminaire through the connectingmember 80 (in more detail, when the conductive plate 71 and the body 90of the luminaire are connected to each other by interposing theconnecting member 80 between the conductive plate 71 of the chipmounting member 70 and the body 90 and heating the connecting member80), and it is possible to prevent an increase and generation ofvariation of the heat resistances due to lack of adhesion. As a result,as compared with the case where the LED chip 10 is mounted to a circuitboard and a rubber sheet-shaped heat radiation sheet such as Sarcon(registered trademark) is disposed between the circuit board and thebody 90 of the luminaire as in the prior art, it is possible to reducethe heat resistance from the LED chip 10 to the body 90 of the luminaireand the heat radiation property can be enhanced. And also, the variationof the heat resistance is reduced, and a rise of a junction temperatureof the LED chip 10 can be prevented. So, it is possible to increase theinput power to increase the power of the light output. As to theconnecting member 80, for example, when the effective contact area forheat conduction to the body 90 of the luminaire is 25 mm² and thethickness of the connecting member 80 is 0.1 mm, in order to control theheat resistance of the connecting member 80 to 1 K/W or less, thethermal conductivity of the connecting member 80 has to be 4 [W/m·K] ormore, and when the epoxy resin sheet highly filled with fused silica asdescribed above is adopted, it can satisfy the condition.

The sub-mount member 30 interposed between the LED chip 10 and theconductive plate 71 is not indispensable when the difference in linearexpansion coefficient between the LED chip 10 and the conductive plate71 is relatively small. When the sub-mount member 30 is not interposedbetween the LED chip 10 and the conductive plate 71, a distance betweenthe LED chip 10 and the bottom wall 90 a of the metal body 90 of theluminaire becomes shorter, whereby the heat resistance from thelight-emitting part 12 of the LED chip 10 to the body 90 is more reducedand the heat radiation property is more increased. So, it is possible toincrease the power of the light output more.

Second Embodiment

Hereinafter, a light-emitting device of this embodiment will beexplained with reference to FIG. 5 to FIG. 11.

The light-emitting device 1 of the present embodiment is generallyconfigured in the same manner as that of the first embodiment, butunlike the first embodiment, it includes a dome-shaped optical member160, a sealing part 150, and a dome-shaped color converting member 170.The dome-shaped optical member 160 controls the distribution of lightemitted from the LED chip 10, and it is made of a translucent material,and is fixedly attached to one surface side (the upper surface side inFIG. 5) of the chip mounting member 70 in such a way that the LED chip10 is housed between the dome-shaped optical member 160 and the chipmounting member 70. The sealing part 150 is made of an encapsulationresin and has a translucency and an elasticity, and it seals the LEDchip 10 and a plurality of (four in this embodiment) bonding wires 14that are electrically connected to the LED chip 10 in the spacesurrounded by the optical member 160 and the chip mounting member 70.The dome-shaped color converting member 170 is a molding made of atranslucent material and a phosphor which emits a light having a colordifferent from an emission color of the LED chip 10 when excited by thelight emitted from the LED chip 10 and passed through the sealing part150 and the optical member 160. The dome-shaped color converting member170 is disposed on the one surface side of the chip mounting member 70in such a way that an air layer 180 is formed between the dome-shapedcolor converting member 170 and a light output surface 160 b of theoptical member 160. Similar parts to the first embodiment are identifiedby the same reference character and no duplicate explanation is madehere.

A chip mounting member 70 of the present embodiment includes aconductive plate 71 in the form of a rectangular plate on which the LEDchip 10 is mounted via the sub-mount member 30, and a wiring board 74which is a flexible printed wiring board in the form of a rectangularplate and is fixedly attached to one surface side of the conductiveplate 71 via a polyolefin-based fixing sheet 79 (see FIG. 6). The chipmounting member 70 includes conductor patterns 73, 73 which are providedon a surface of the wiring board 74 on the conductive plate 71 side viathe insulating part 72 made of insulating substrate and are electricallyconnected to the LED chip 10. The insulating part 72 has a window hole75 at the center thereof for partially exposing one surface of theconductive plate 71, and the LED chip 10 is mounted to the conductiveplate 71 via the sub-mount member 30 arranged inside the window hole 75.The insulating part 72 of the wiring board 74 is made using a polyimidefilm, and each of the conductor patterns 73, 73 is configured as amulti-layered film including a Cu film, a Ni film, and an Au film.

The wiring board 74 has a resist layer 76 laminated on a surface on theopposite side of the conductive plate 71, and the resist layer 76 ismade of a white resin for reflecting the light emitted from the LED chip10.

In this embodiment, the sub-mount member 30 is made of AIN that has arelatively high thermal conductivity and an insulating property. The LEDchip 10 has anode electrodes 13 a formed at two adjacent corners on onesurface side thereof (see FIG. 7 and FIG. 8A), and has cathodeelectrodes 13 b formed at the other two corners thereof (see FIG. 7 andFIG. 8A). Each of the anode electrodes 13 a is electrically connected toone of the conductor patterns 73 via a bonding wire 14, and each of thecathode electrodes 13 b is electrically connected to the other of theconductor patterns 73 via another bonding wire 14. The resist layer 76of the wiring board 74 is patterned so as to expose two portions of eachof the conductor patterns 73 near the window hole 75 and also expose onepart of each of the conductor patterns 73 at the peripheral part of thewiring board 74. In each of the conductor patterns 73, the two portionsexposed near the window hole 75 form terminal parts 73 a to be connectedto bonding wires 14, and the circular portions exposed at the peripheralparts of the resist layer 76 form electrode sections 73 b to beconnected to the exterior. Out of the two electrode sections 73 b, theelectrode section 73 b to which each anode electrode 13 a of the LEDchip 10 is electrically connected (the right electrode section 73 b inFIG. 7) has a mark “+” thereon, and the electrode section 73 b to whicheach cathode electrode 13 b of the LED chip 10 is electrically connected(the left electrode section 73 b in FIG. 7) has a mark “−” thereon,which enables a visual recognition of the polar of the electrodesections 73 a, 73 b in the light-emitting device 1, whereby it ispossible to prevent an error connection.

In the present embodiment, the window hole 75 in the wiring board 74 isformed into a rectangular shape, as shown in FIG. 8A, and the terminalparts 73 a are provided around at the middle of each side of therectangular window hole 75. But, as shown in FIG. 8B, when the terminalparts 73 a are formed near one end of each side of the window hole 75,respectively, it is possible to lengthen the entire length of eachbonding wire 14, whereby it is possible to increase the reliability ofthe device.

The LED chip 10 and the sub-mount member 30 may be connected to eachother by using a solder, such as SnPb, AuSn, and SnAgCu, or silver pastefor example, but preferably they are connected to each other by using aPb-Free solder such as AuSn and SnAgCu.

The encapsulation resin used to make the sealing part 150 is a siliconeresin, but the material is not limited to a silicone resin, and anacrylic resin may be used for example.

The optical member 160 is a molding of a translucent material (forexample, silicone), and is formed in a dome shape. In this embodiment,since the optical member 160 is a silicone molding, it is possible toreduce differences in refractive index and linear expansion coefficientbetween the optical member 160 and the sealing part 150. When thesealing part 150 is made of an acrylic resin, it is preferable that theoptical member 160 is also made of the acrylic resin.

Furthermore, the optical member 160 is configured so that the lightoutput surface 160 b has a convex surface which does not totally reflectthe light entered therein from a light incident surface 160 a at theboundary between the light output surface 160 b and the air layer 180,and the optical member 160 is arranged so that the light axis thereof isaligned with that of the LED chip 10. Therefore, the light emitted fromthe LED chip 10 and entered in the light incident surface 160 a of theoptical member 160 is not totally reflected at the boundary between thelight output surface 160 b and the air layer 180, and it becomes easyfor the light to reach the color converting member 170, whereby it ispossible to increase the whole light flux. The light emitted from thesides of the LED chip 10 is propagated in the sealing part 150, theoptical member 160, and the air layer 180, and reaches the colorconverting member 170, and the light excites the phosphor of the colorconverting member 170 or passes through the color converting member 170without hitting the phosphor. The optical member 160 is formed to have auniform thickness along the direction normal to the optical member 160independently of the positions thereof.

The color converting member 170 is a molding of a mixture of atranslucent material, such as silicone, and a particulate yellowphosphor which is excited by the blue light emitted from the LED chip 10and emits broad yellowish light (that is, the color converting member170 contains a phosphor). Therefore, in the light-emitting device 1 ofthis embodiment, the blue light emitted from the LED chip 10 and thelight emitted from the yellow phosphor are both emitted through theouter surface 170 b of the color converting member 170, whereby a whitelight can be obtained. The translucent material used for the colorconverting member 170 is not limited to silicone, and acrylic resin orglass may be adopted, for example. Also, the phosphor which is mixed tothe translucent material used as the material of the color convertingmember 170 is not limited to a yellow phosphor, and for example, a redphosphor or a green phosphor may be mixed to obtain the white light.

In the color converting member 170, an inner surface 170 a is formed tofollow the shape of the light output surface 160 b of the optical member160. Therefore, the distance between the light output surface 160 b andthe inner surface 170 a of color converting member 170 is generally asteady value along the direction normal thereto independently of thepositions of the light output surface 160 b of the optical member 160.The color converting member 170 is molded to have a uniform thicknessalong the direction normal to the color converting member 170independently of the positions thereof.

In the light-emitting device 1 of the present embodiment, since the airlayer 180 is formed between the color converting member 170 and theoptical member 160, when an external force acts on the color convertingmember 170, a possibility that the color converting member 170 isdeformed by the external force and makes contact with the optical member160 is reduced, So, it can be prevented that the stress applied to thecolor converting member 170 by the external force is transmitted to theLED chip 10 and each bonding wire 14 via the optical member 160 and thesealing part 150. Therefore, variations in light emitting property ofthe LED chip 10 and disconnection of each bonding wire 14 due to theexternal force are less likely to occur, and the reliability can beincreased. In addition, the air layer 180 formed between the colorconverting member 170 and the optical member 160 provides advantagesthat moisture in the ambient atmosphere does not easily reach the LEDchip 10, and that the amount of light which is emitted by the LED chip10 and passes through the sealing part 150 and the optical member 160and enters the color converting member 170 and then is scattered by thepowder of yellow phosphor in the color converting member 170 toward theoptical member 160 and passes through the optical member 160 is reduced,and as a result, the light output efficiency of the light-emittingdevice 1 to the exterior can be increased as a whole.

In the light-emitting device 1 of this embodiment, the thicknessdimension of the sub-mount member 30 is set so that the surface of thesub-mount member 30 is more separated from the conductive plate 21 thanthe surface (the surface of the resist layer 76) of the wiring board 74,thereby the light emitted from the LED chip 10 to the side direction canbe prevented from being absorbed to the wiring board 74 through theinner surface of the window hole 75 formed in the wiring board 74.

Meanwhile, as to a method for manufacturing the above describedlight-emitting device 1, for example, conceivable is a method in whichthe LED chip 10 and each of the conductor patterns 73, 73 areelectrically connected to each other via two bonding wires 14,respectively, and after that, as shown in FIG. 7, a tip of a nozzle 401of a dispenser 400 is positioned in a resin injection hole 78 formed incommunication with the window hole 75 in the wiring board 74, and then aliquid encapsulation resin (for example, a silicone resin) is injectedinto a gap between the sub-mount member 30 and the wiring board 74, andis cured to form a part of the sealing part 150, and the liquidencapsulation resin (for example, a silicone resin) to be the remainingpart of the sealing part 150 is injected again into the dome-shapedoptical member 160 and the optical member 160 is arranged at apredetermined position on the chip mounting member 70, and then theencapsulation resin is cured to from the sealing part 150 and to fix theoptical member 160 to the chip mounting member 70 at the same time, andthen the color converting member 170 is fixedly attached to the chipmounting member 70. In such a manufacturing method, since air bubbles(voids) may be formed in the sealing part 150 during the manufacturingprocess, it is necessary to inject an excess amount of the liquidencapsulation resin into the optical member 160. However, if such amethod is adopted, when the optical member 160 is arranged at apredetermined position on the chip mounting member 70, a part of theliquid encapsulation resin overflows out of the space surrounded by theoptical member 160 and the chip mounting member 70 and spreads over thesurface of the resist layer 76, which forms an unnecessary encapsulationresin part, whereby light may be absorbed or diffused reflection oflight may be caused due to the uneven surface thereof, and the lightoutput efficiency of the light-emitting device 1 as a whole may bereduced.

Thus, in the light-emitting device 1 of this embodiment, a plurality ofresin reservoir holes 77 for reserving the encapsulation resinoverflowed from the space surrounded by the optical member 160 and thechip mounting member 70 are formed separately in the outer peripheraldirection of the cal member 160 on the surface of the chip mountingmember 70 between a portion on which a ring-shaped end of the opticalmember 160 is overlapped and a portion on which a ring-shaped end of thecolor converting member 170 is overlapped. The resin reservoir hole 77is comprised with a through hole 77 a formed in the wiring board 74 anda recess 77 b formed in the conductive plate 71 at a positioncorresponding to the through hole 77 a. Furthermore, in thelight-emitting device 1 of this embodiment, a ring-shaped lightabsorption prevention substrate 40 is disposed on the surface of thechip mounting member 70 between the portion on which the ring-shaped endof the optical member 160 is overlapped and the portion on which thering-shaped end of the color converting member 170 is overlapped tocover each of the resin reservoir holes 77, and the light absorption bythe resin part which is formed by the encapsulation resin reserved andcured in each of the resin reservoir holes 77 can be prevented by thelight absorption prevention substrate 40. In the light absorptionprevention substrate 40, a white resist layer for reflecting the lightfrom the LED chip 10, the color converting member 170 and so on isprovided on the surface opposite to the chip mounting member 70 side,whereby the above described light absorption can be prevented. The lightabsorption prevention substrate 40 may be disposed on the surface sideof the chip mounting member 70 after the encapsulation resin whichoverflows when the optical member 160 is arranged at a predeterminedposition on the chip mounting member 70 fills each of the resinreservoir holes 77, and then it may be fixed to the chip mounting member70 by the encapsulation resin when the encapsulation resin is cured. Inthe light absorption prevention substrate 40, a plurality of cutouts 42for exposing a small region of each of the resin reservoir holes 77 areformed to prevent that voids are generated when the encapsulation resinin the resin reservoir holes 77 is cured.

In the light-emitting device 1 of this embodiment, as is the case withthe first embodiment, the sheet-shaped connecting member 80 disposed onthe other surface side of the conductive plate 71 for connecting theconductive plate 71 to the body 90 of the luminaire which is a metalmember for holding the chip mounting member 70 and having an electricalinsulating property and thermally connecting the conductive plate 71 andthe body 90 to each other is provided. So, as compared with the casewhere a rubber sheet-shaped heat radiation sheet is disposed between thebody 90 and the plate, it is possible to reduce the heat resistance fromthe light-emitting part of the LED chip 10 to the metal member forholding the chip mounting member, whereby the heat radiation propertycan be enhanced, variation of the heat resistances can be reduced, and arise of a junction temperature of the LED chip can be constrained.Therefore, it is possible to increase the input power and to increasethe power of the light output.

In addition, in the light-emitting device 1 of this embodiment, theconnecting member 80 has a plane size larger than that of the conductiveplate 71. So, as compared with a case where the connecting member 80 andthe conductive plate 71 are formed to have the same plane size, it ispossible to lengthen a creepage distance between the conductive plate 71and the body 90 of the luminaire which is a metal member, so that it ispossible to enhance a lighting surge protection when the device is usedas a light source of a luminaire (it is noted that an indoor luminaireand an outdoor luminaire generally require different creepage distancesbetween a light-emitting device and a metal member, and an outdoorluminaire requires a longer creepage distance). As to the thickness ofthe sheet-shaped connecting member 80, it is necessary to design thethickness depending on a withstanding pressure which is required forlighting surge protection, but a smaller thickness is desirable in termsof a lower heat resistance. Therefore, as to the connecting member 80,the plane size may be set to satisfy the requirement of the creepagedistance after the thickness of the connecting member 80 is set.

In the luminaire described in the first embodiment, each of thelight-emitting devices 1 is connected by means of the leads 93 (see FIG.1 and FIG. 4), but in the luminaire of this embodiment, as shown in FIG.10 and FIG. 11, a circuit board 300 including an insulating substrate301 on which a wiring pattern 302 is formed on one surface thereof fordefining the connection between the light-emitting devices 1 isprovided. In this embodiment, a plurality of light-emitting devices 1are connected in series, but the connection type of the light-emittingdevices 1 is not particularly limited to that. For example, thelight-emitting devices 1 may be connected in parallel, or a seriesconnection and a parallel connection may be combined.

The circuit board 300 is disposed separately from the bottom wall 90 aof the body 90 in the luminaire, and has opening windows 304 formed inpositions thereof corresponding to the light-emitting devices 1 forinserting a part of the light-emitting device 1, respectively. Theinsulating substrate 301 of the circuit board 300 may be made of a glassepoxy resin such as FR4, but the material is not limited to the glassepoxy resin, and may be a polyimide-based resin or a phenolic resin forexample.

The above described circuit board 300 has a wire insertion hole 306which is formed therethrough for inserting leads for power supply whichare inserted through the insertion hole 90 c formed through the bottomwall 90 a of the body 90, and a pair of wires inserted through the wireinsertion hole 306 is electrically connected to the circuit board 300.The circuit board 300 further has a light reflecting layer 303, which isa white resist layer, formed on a surface side opposite to the bottomwall 90 a of the body 90 side, and the most part of the wiring pattern302 is covered with the light reflecting layer 303.

In the circuit board 300, each opening window 304 has a plane size whichis slightly larger than that of the chip mounting member 70 of thelight-emitting device 1. In the light-emitting device 1 of the presentembodiment, the chip mounting member 70 has chamfered parts at the fourcorners in a plan view to round the corners, and as compared with thetwo chamfered parts near the electrode sections 73 b (the right and leftchamfered parts in FIG. 7), the remaining two chamfered parts (the topand bottom chamfered parts in FIG. 7) are designed to have a largerradius curvature. So, it is possible to increase a region area in whichthe wiring pattern 302 can be formed on the surface of the circuit board300. The circuit board 300 is provided with a surface-mounted Zenerdiode 331 for over voltage protection (see FIG. 11) and asurface-mounted ceramic capacitor 332 (see FIG. 11) near each of theopening windows 304 in order to prevent an application of an overvoltage to the LED chip 10 of the light-emitting device 1.

In the light-emitting device 1 of the present embodiment, each electrodesection 73 b of the chip mounting member 70 is electrically connected tothe wiring pattern 302 of the circuit board 300 via the terminal plate310. The terminal plate 310 is folded at one end of the elongated metalplate into an L shape to form a terminal strip 311 which is connected tothe wiring pattern 302 in such a way that the terminal strip 311overlaps the wiring pattern 302 in the thickness direction, and theterminal plate 310 is folded at the other end thereof into a J shape toform a terminal strip 312 which is connected to the electrode section 73b in such a way that the terminal strip 312 is fixed to the electrodesection 73 b in the thickness direction. Therefore, it is possible torelieve the stress applied to connection parts between the connectingterminal 310 and the electrode section 73 b and between the connectingterminal 310 and the wiring pattern 302 due to a difference in linearexpansion coefficient between the body 90 and the circuit board 300,thereby it is possible to increase the connection reliability betweeneach light-emitting device 1 and the circuit board 300.

In the above described Embodiments, each of the light-emitting devices 1is provided with the connecting member 80, but the connecting member 80may have a larger plane size, and a plurality of light-emitting devices1 may commonly use the connecting member 80.

1. A light-emitting device comprising: a LED chip; a chip mountingmember having a heat transfer plate and a conductor pattern: said heattransfer plate being made of a heat conductive material and one surfaceside of which said LED chip is mounted on, said conductor pattern beingformed on the one surface side of said heat transfer plate through aninsulating part and electrically connected to said LED chip; asheet-shaped connecting member disposed on the other surface side ofsaid heat transfer plate to connect said heat transfer plate to a metalmember for holding said chip mounting member, said connecting memberhaving an electrical insulating property and connecting said heattransfer plate and said metal member thermally to each other; a sealingpart which is made of an encapsulation resin and seals the LED chip; anoptical member which has a convex light output surface and is piled onthe sealing part; and a dome-shaped color converting member which is amolding made of a translucent material and a phosphor, the phosphoremitting a light having a color different from an emission color of theLED chip when excited by the light emitted from the LED chip, the colorconverting member covering the optical member from the light outputsurface side of the optical member, the color converting member beingarranged so that an air layer is formed between the light output surfaceand the color converting member, wherein said connecting member is madeof an epoxy resin sheet which includes a filler and whose viscosity isreduced by heating, and wherein said epoxy resin sheet has a highflowability in heating.
 2. The light-emitting device as set forth inclaim 1, wherein said LED chip has a light-emitting part made of aGaN-based compound semiconductor material on a main surface side of aconductive substrate formed from a SiC substrate or a GaN substrate. 3.The light-emitting device as set forth in claim 1, further comprises asub-mount member which is larger in chip size than said LED chip and isdisposed between said LED chip and said heat transfer plate to relieve astress applied to said LED chip due to a difference in linear expansioncoefficient between said LED chip and said heat transfer plate.
 4. Thelight-emitting device as set forth in claim 1, wherein said connectingmember has a plane size larger than that of said heat transfer plate.